Do only the non Immigrant Visa from home .Then you Go to Thailand and open a bankaccount and deposit the 400k and apply for the extention at your Immigration office.You only need a traveller isurance for the 90 day Visa.This is the easiest way to get the extention.
Where there any Problems with the Immigration office or was it uncomplicatet?I think I have to bring a Bankstatement of the income of the last months.Is that right?
No.The money has to be on an account wich is available every time.I heard of people who had to take money from the account at an ATM and show the bill to the Immigration.